Autoimmune diseases are disorders in which an individual's immune system targets and destroys apparently normal tissue Autoimmune diseases include rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), scleroderma (SCL), Sjogren's syndrome (SjS), polymyositis (PM), dermatomyositis (DM), mixed connective tissue disease (MCTD) and pemphigus vulgaris (PV). Autoantibodies are commonly directed against cellular proteins and nucleic acids. In certain diseases, such as PV, the target of autoantibodies is known and the autoantibody is thought to play a role in the pathogenesis of the disease. In other diseases, such as SLE, the target of many different autoantibodies have been identified but the role of autoantibodies in the pathogenesis of SLE is as yet uncertain.
Detection of autoantibodies in the serum of patients assists in the diagnosis of autoimmune diseases. Rheumatoid factor (IgM antibodies directed against human IgG) is detected in the majority of patients with RA and supports that diagnosis in a given individual (Kelly, W.N., et al. 1985. Textbook of Rheumatology. 2nd ed. Saunders. pp. 667). Antinuclear antibodies (ANA) are present in approximately 98% of individuals with active SLE. Although ANA are not specific for the diagnosis of SLE, the absence of these antibodies argues against the diagnosis of SLE in a given patient (Kelly et al., 1985 supra pp. 691).
Sjogren's syndrome (SjS) is an autoimmune disease characterized by a chronic inflammation and destruction of lacrimal and salivary glands that results in dry eyes and mouth. SjS may affect other organs including the lungs, kidneys, liver and central nervous system, and may be associated with vasculitis, cryoglobulinemia, increased incidence of lymphoma, and macroglobulinemia (Talal, N., 1988. Primer in the Rheumatic Diseases, 9th ed. Schumacher, R. H., eds. pp 136-138). The disease can occur in the absence of other connective tissue diseases ("primary" SjS) or can be associated with RA, SLE, SCL and PM ("secondary" SjS).
Up to 30% of patients with rheumatoid arthritis, 10% of patients with SLE, and 1% of patients with SCL have been reported as having secondary Sjogren's syndrome. Immunogenetic predisposition appears to play an important role in the incidence of Sjogren's syndrome.
ANA are detected in between 50 and 80% of patients with SjS. Antibodies directed against nucleoprotein antigen SS-B/La are also detected in many patients with SjS. Antibodies directed against SS-A/Ro are also detected in patients with this disorder (Talal, 1988, supra 136-138).
A diagnosis of Sjogren's syndrome is made when the triad of keratoconjunctivitis sicca, xerostomia, and mononuclear cell infiltration of the salivary gland is noted (Talal, 1988, suora pp. 136-138). This last finding is made by a lower lip biopsy. Treatment is geared toward symptomatic relief of mucosal dryness and meticulous oral hygiene, and includes artificial tears, ophthalmologic lubricating ointments, nasal sprays of normal saline, frequent sips of water, and oral fluoride treatments. There is currently no effective treatment for the ongoing exocrine gland destruction.